I'm reading / working through the QCAD book and tried some text sequences. When I insert them with the property editor or dimension dialog fields, they work. However, if I try to put them in a text block or add them to a dimension after the fact, they're treated literally. For example:

I thought I might have the syntax wrong, so I copied the examples on the left from the QCAD PDF (pasted into a text editor first, then recopied to verify no hidden characters were captured). The dimensions on the right were done in property editor fields and they work, but based on a previous attempt if I were to remove the tolerances and enter them as S\<superscript\<subscript>;, they'll show up literally as on the left.

I created the text entities and pasted the escape sequences directly into the source window of the text editor: